Shinji Kaneiwa

Liquid phase epitaxial growth of In1−xGaxP1−yAsy On GaAs substrates

In1−xGaxP1−yAsy layers were grown on GaAs substrates by LPE at 700°C. A great difference was found between the growth on (100) and (111)B substrates. On (100) substrates, mirror-like In1−xGaxP1−yAsy (y > 0.01) layers had flat interfaces but their surfaces were rough. On the other hand, mirror-like In1−xGaxP1−yAsy(0 ≦ y ≲ 0.5) layers were obtained on (111)B substrates with a smallest match of about 0.5%. The composition range of mirror-like layers was dependent on the substrate orientation. The results indicate that the immiscible region of the epitaxial layer on the (100) face is wider than that on the (111)B face.

Improvement of high-power characteristics of 780-nm AlGaAs laser diode by (NH4)2S facet treatment

Coherent cw operation has been obtained with a 10x4 array of Grating Surface Emitting (GSE) lasers consisting of 40 lasers and 50 emitting sections. The array is a GaAs quantum well device, grown on an A1GaAs substrate, operating at 861 nm to which the substrate is transparent. It is mounted p-down to metallized traces on a BeO slab to provide isolated electrical contacts and thermal contact to a simple chilled-water cooler. A single spectral line 0.5 A wide indicates coupling of the 40 laser sections. More detailed measurements on a section of an array containing ten laterally coupled lasers, 20 outputs, show that it is operating at a junction temperature of 30°C, has a line width of 0.1 5A, and a measured coherence of >75%. The expected wavelength stabilization with temperature due to the DBR grating is found, with a value of =0.6A/°C. An array of 4 longitudinally coupled lasers produced a line width of 130MHz and evidence of high coherence.

Room‐temperature cw operation of InGaPAs/GaAlAs visible light double heterojunction lasers

InGaPAs/GaAlAs double heterojunction (DH) lasers operated continuously at room temperature in the spectral range of 720–730 nm. The DH structure was grown on a GaAs substrate by liquid phase epitaxy, and the laser diode fabrication was the same as V‐channeled substrate inner stripe lasers. The lowest values of a threshold current (Ith) were 145 and 186 mA under pulsed and cw operation, respectively. The characteristic temperature T0 of the Ith was typically 120 K. It was confirmed that the InGaPAs/GaAlAs system has sufficient band‐gap energy difference between the active layer and the cladding layer. Multiple longitudinal and fundamental transverse modes were obtained.

High-Power CW Operation in V-Channeled Substrate Inner-Stripe Lasers with “Torch”-Shaped Waveguide

High-power AlGaAs lasers with a waveguide pattern like a torch have been grown by a two-step liquid-phase epitaxy process. The waveguide pattern consists of a 6 µm-wide region about 220 µm long and a 10 µ-wide region about 20 µm long connected by a tapered region about 10 µm long. A stable fundamental transverse mode has been obtained of up to more than 200 mW output power in a 4%–95% coated device in the wavelength range of 830 nm. The lasers have extremely high reliability, and stable continuous operation for over 4000 hours has been confirmed at 50°C, 50 mW with no obvious degradation.

Integrated optic disc pickup

The present status of waveguide-type integrated-optic disc pickups are reviewed. The authors have proposed and fabricated several types, and have demonstrated their fundamental functions. For the ROM pickup, they successfully reduced the focused spot to a diameter that is slightly larger than the diffraction-limited value, and confirmed capability of the focusing/tracking error signal detection. The pickup was extended to that for magneto-optical (MO) disc system, and the MO pickup was found experimentally to detect a polarization rotation as small as one contained in the signal beam reflected from MO medium. The pickup for parallel-data cards was also fabricated with photodiode array, and seven-track parallel readout was demonstrated. It was found by theoretical analysis that the waveguide-FGC combined type pickup has the possibility of super-resolution readout.